Field of the Invention
The present invention relates to an A/D conversion device which converts analog quantities to digital quantities.
Description of the Related Art
Heretofore, there has been a CPU which holds a plurality of A/D converters which convert analog quantities to a form of digital quantities which a CPU (Central Processing Unit) or the like can use. In recent years, analog signals which the CPU inputs with one system are increasing, and the absolute number of A/D converters (A/D ports in the CPU) is deficient. Thus, for example, as is disclosed in JP-A-2007-333574 (PTL 1), a method whereby items of information inputted into an A/D converter are selectively switched and used by using an interface circuit is adopted.
The usage pattern of the A/D converter disclosed in PTL 1 is such that a plurality of items of information to be inputted are selectively switched by a switch and inputted into an MPU (Micro-processing unit). This configuration enables the number of items of input information to be increased without increasing the number of A/D converters.
However, this kind of heretofore known device is simply such as to suppress the number of A/D converters, and in this system, as a switch which switches items of input information is added, it is also necessary to enhance a failure diagnosis function for the switch, and in this case, the necessity cannot help but be met by providing an additional circuit separately.
Thus, the present inventors and others have proposed an A/D conversion device wherein it is possible to add a failure diagnosis function without increasing the number of A/D converters and without providing an additional circuit, as disclosed in JP-A-2013-225781 (PTL 2).
PTL 1: JP-A-2007-333574
PTL 2: JP-A-2013-225781
In the A/D conversion device disclosed in PTL 2, the number of A/D converters can be suppressed, but it is impossible to detect anomalies of the A/D converter itself and a device connected to the A/D converter, and the necessity for the anomaly detection has arisen.